Liquid, and especially concentrated liquid pharmaceutical compositions offer many advantages over solid compositions. Liquids are easy to swallow and provide an excellent vehicle for the uniform delivery of pharmaceutical actives. Liquids provide a rapid onset of pharmacologic action, since the composition does not first have to disintegrate and dissolve in the gastrointestinal tract. Concentrated liquid compositions are ideally suited for encapsulation within a soft gelatin shell, to provide a portable and easy-to-swallow soft, flexible capsule. Encapsulation would also permit the accurate and uniform delivery of a unit dose of a pharmaceutical active, an advantage which becomes especially important when relatively small amounts of an active are to be delivered. Additionally, soft gelatin capsules are aesthetically appealing (especially when filled with a transparent liquid) and can be manufactured in a wide variety of sizes, shapes, and colors.
However, despite these advantages of liquid compositions, it is not always possible to prepare a liquid composition of the desired pharmaceutical active. In many instances the components to be solubilized are not compatible with one another, or require higher solvents. Also, it may not be possible or desirable to incorporate water, water-miscible co-solvents, or surfactants into a pharmaceutical composition. For example, certain water-miscible co-solvents may be relatively volatile, thereby resulting in concentration changes in the actives over time. Also, these co-solvents may not be compatible with the desired pharmaceutical actives.
Previous investigators have attempted to circumvent these incompatibility problems by modifying the gelatin in the capsule shell. For example, U.S. Pat. No. 3,865,603, to Szymanski et at., issued Feb. 11, 1975 discloses gelatin compositions which are extended with chemically modified fluidity starches; U.S. Pat. No. 2,580,683, to Kreuger, issued Jan. 1, 1952 discloses gelatin compositions modified by the addition of non-hygroscopic water soluble substances; and Japanese Patent No. 84044096, to Morishita, issued Jan. 26, 1984 discloses gelatin shells modified with tannic acid, and sugar and/or sugar derivatives. However, it may not always be desirable, feasible or economical to modify the soft gelatin shell with such additives. The present inventor has found incorporating a specific component in the outer gelatin shell, i.e., a xanthine derivative overcomes incompatability problems with an analgesic active.
It is therefore an object of the present invention to provide a soft gelatin capsules containing an analgesic pharmaceutical actives and xanthine or xanthine derivative wherein said xanthine or xanthine derivative is incorporated into the gelatin shell.
These and other objects of this invention will become apparent in light of the following disclosure.